What is a Peptide?
Peptides are short chains of amino acids linked by peptide bonds. Typically, peptides contain less than 50 amino acids. Anything longer is considered a protein.
Peptides serve many important biological functions. For example:
- Some peptides act as chemical messengers and play roles in cell signaling, communication between cells, and regulation of bodily functions. These messenger peptides are also called peptide hormones. Examples include insulin and oxytocin.
- Other peptides play key roles in the immune system, defending the body against bacteria, viruses, and cancer cells. These include small signaling peptides called cytokines, as well as larger peptide fragments that make up antibodies.
- Peptides can also have antimicrobial effects, killing or inhibiting the growth of microorganisms. Antimicrobial peptides protect the skin and membranes from infection.
- Bioactive peptides derived from food proteins can positively impact health. For instance, some food-derived peptides demonstrate antihypertensive effects that may help reduce high blood pressure.
How are peptides formed?
Peptides are assembled when the bonds between amino acids are formed through a dehydration reaction. The carboxyl group of one amino acid bonds with the amino group of another amino acid, releasing a molecule of water. This forms a peptide bond.
The sequence and number of amino acids in a peptide determine its structure and function. The unique order of amino acids gives each peptide a specific shape and physiological role.
Where are peptides found?
Peptides occur naturally in many living organisms. For instance:
- Animal, plant, and microbial proteins contain peptide fragments. Peptides are liberated when proteins are broken down during digestion or by proteolytic enzymes.
- Many peptides serve signaling functions in organisms and are called peptide hormones, neurotransmitters, growth factors, and cytokines.
- Bioactive peptides also occur in some foods, especially dairy and meat. These food peptides are inactive within the parent protein but can be liberated during digestion or processing.
In summary, peptides are short amino acid chains that play vital roles in cell communication, immunity, antimicrobial defense, and food functionality. Understanding peptide structure and biology is crucial, as peptides show promise in drug development and enhancing nutrition.